GB-A-2156727 (Pemberton Sintermatic SA) discloses a method for the production of helical protein products in which a proteinaceous product, such as meat or a meat-like product is injected into a cylindrical mould through a nozzle. As extrusion proceeds, the nozzle is withdrawn from the mould to form said helical product. Optionally the mould and nozzle may be rotated relative to one another, but according to GB-A-2156727 this is not necessary provided the rates of extrusion and nozzle withdrawal are correctly adjusted. The wall of the mould is porous and as the product is formed in the nozzle, an acid is applied through the wall onto the outer surfaces of the product, which acid causes coagulation of the proteinaceous product at the surface so as to render the surface cohesive, by which is meant that the product becomes self-supporting, so that thereafter it can retain its shape.
A problem with the method of GB-A-2156727 is that by forming in situ a cohesive skin on the surface of the product by the application of acid or heat, the adjacent turns of the product tend to stick together where they touch to form a generally cylindrical product having a ribbed appearance. Areas of the surface that are inadvertently missed with the acid or heat treatment during manufacture tend to re-anneal during subsequent cooking of the product.
Another disadvantage of the method of GB-A-2156727 is that it does not permit the continuous manufacture of product. Each helical unit has to be made individually within the mould, and removed from the mould before the next unit can be formed. Furthermore, it is difficult to adjust the extrusion and nozzle withdrawal rates suitably to obtain an helical product.
Accordingly it is an object of the present invention to provide a skinless, helical food product in which the adjacent turns are substantially prevented from re-annealing during manufacture or subsequent cooking.
Another object of the invention is to provide an improved method of manufacturing an helical food product.
A particular, ancillary object of the present invention is to provide a continuous process for manufacturing an helical food product, which process should ideally be easy to set-up and operate with minimum wastage.
Yet another object is to provide an improved apparatus for implementing the method of the invention.
According one aspect of the present invention therefore there is provided a food product comprising one or more plastic food substrates formed into an helical configuration and coated with a fluid barrier agent to prevent re-annealing of adjacent turns of the product.
By xe2x80x98helicalxe2x80x99 is meant a single helix or a multiple helix, e.g. a double or triple helix. Said food product may be formed from a single plastic food substrate as a single or multiple helix. Alternatively a multiple helix food product may be made from a plurality of different food substrates, typically two, three or four such substrates.
The fluid barrier agent acts to prevent bonding of the food substrate(s) in adjacent turns of the helical product during subsequent processing steps, including cooking. Said fluid barrier agent may be a liquid vegetable oil such, for example, as hydrogenated vegetable oil, Soya oil, rape oil, sunflower oil, safflower oil, peanut oil or a mixture of such oils. Alternatively, said fluid barrier agent may comprise an oil and water emulsion. Such an emulsion may comprise approximately equal amounts of oil and water, together with a suitable emulsifying and/or stabilising agent. Said emulsion may be formed by ambient or chilled temperature high shear mixing using Soya protein isolate; milk protein (caesinates) lactose/milk minerals; milk protein with stabilizers, Xanthan gum, Guar gum and/or deheated mustard power; or blood plasma. At higher energies and temperatures, sodium stearoyl lactoylate can be used. Alternatively the emulsion could be prepared using polyglycol alginates. Higher energy systems of emulsification, by application involve the dispersion of an emulsifying agent into a fraction of the liquid oil phase heated above the melting point of the emulsifying agent. The dispersed emulsifier, in oil, is then introduced into the bulk oil and mixed, and finally introduced by high shear into the water phase, neat or with the water optionally pre-stabilised with gums such as Xanthan, Guar or other hydrocolloids such as hydroxypropylmethyl cellulose or modified celluloses, carrageenans, starches, alginates or gelatin.
Said emulsifying agent may be selected from lipophilic mono and di glycerides of fatty acid, or acetic acid, lactic acid, citric acid, tartaric acid esters of glyceride or a blend thereof, e.g. E471, E472 (a), (b), (c), (d), (e), (f). Alternatives include the lecithins.
Said fluid barrier agent may optionally carry one or more additives selected from water or oil soluble seasonings and flavouring components.
The or each plastic food substrate may, for example, be selected from meat, cheese and pastry based doughs. Preferably at least one of the substrates will be meat based. Said meat may be fresh or frozen, finely comminuted or mechanically separated (recovered) meat. Said meat may be animal or poultry meat, and may be lean meat or, preferably, a mixture of lean meat and fat. Such meat-based substrates may comprise 25-100 wt % meat, preferably 50-75 wt %, including fat. For example a meat-based substrate may typically comprise about 70% meat. The meat component itself may comprise 60-80 wt % mechanically separated meat, typically about 70 wt %. Said meat based substrate may further comprise 5-15 wt % ice, typically about 12 wt %, and optionally one or more seasonings and flavourings. By xe2x80x9cmeatxe2x80x9d here is meant physical meat. Said physical meat may have an analytic meat content of 60-80%, typically about 70% wt, with the remainder usually being largely water.
In especially preferred embodiments of the present invention, the or each meat-based substrate further comprises one or more water-retaining agents, which serve to retain water within the product on cooking. It will be appreciated by those skilled in the art that, on cooking, meat loses water, which gives rise to shrinkage and weight loss of the product. By including a water-retaining agent within the meat substrate(s), such water loss is reduced. Moreover, those skilled in the art will further recognise that a helix represents a fairly xe2x80x98high energyxe2x80x99 configuration, and on cooking the product will tend to unwind. Such partial unwinding will result in elongation of the product along the longitudinal axis of the helix. Of course, the extent of such elongation would be offset by shrinkage of the product overall as a result of water loss. However, by controlling water loss in accordance with the present invention, an helical product in accordance with the present invention can be produced which, on cooking, exhibits a net expansion. This is a particularly interesting effect, which appeals especially to children.
In some embodiments, said meat substrate may comprise 5-20 wt % of such a water-retaining agent, preferably 8-15 wt %. Said water-retaining agent may comprise a hydratable, dried or partially dried foodstuff that hydrates under product cooking by absorbing water released from the meat. Especially preferred are granular water-swellable agents, which expand on cooking to assist in overall expansion of the helical product.
Said water-retaining agent will preferably comprise one or more carbohydrates. Carbohydrates are preferred as they may also assist in disrupting the meat protein matrix during cooking. Suitable carbohydrates are rusk and starches, e.g. native starch (tapioca). About 13-14 wt % rusk is especially preferred, although the rusk content can be reduced to around 7-8 wt % provided another water-retaining or swelling agent is employed in addition. As water-retaining agents may also be employed fat emulsions stabilized by protein. Said protein may comprise any globular or linear proteins that are known in the art for stabilizing a fat emulsion, such for example as Soya or milk proteins, e.g. Soya protein isolate or caesinates. The meat substrate may comprise up to one part fat emulsion to four parts meat, typically one to six parts. Said fat emulsion will also provide an alternative fat source to the meat itself.
In some embodiments, said meat substrate may comprise collagen fibre; typically 1-3% wt, e.g. 2% wt. It has been found that at ambient temperature up to about 58xc2x0 C. collagen fibre holds water and thus may act as a water retaining agent. On cooking, collagen fibre forms a weak gel or liquid form of gelatin. This relaxing of the structure of the collagen fibre has been found to promote extension of the product as described above. Collagen fibre also assists in preparing a meat substrate that is suitable for extrusion. In some embodiments of the invention collagen fibre may be used in conjunction with carbohydrate (e.g. rusk) as a water-retaining agent.
According to another aspect of the present invention, there is provided a method for making an helical food product in accordance with the present invention, which method comprises extruding one or more plastic food substrates through a nozzle into a hollow shaping part whilst causing or allowing relative rotation of the nozzle and shaping part, thereby to form a product of helical configuration, and applying a fluid barrier agent to the outer surface of the product as it is dispensed from the nozzle into the shaping part, which barrier agent is adapted to prevent re-annealing of adjacent turns of the helical product.
Where two or more food substrates are co-extruded, such substrates may be extruded through juxtaposed dispense passageways in said nozzle.
According to the method of the present invention, the helical product may be collected from the shaping part, treated to make the surface of the product sufficiently rigid for cutting, and then cut to convenient lengths. The crust hardening may be achieved by heat-setting, e.g. by flash-frying, or crust freezing. Conveniently, crust freezing may be effected by passing the product through a cryogenic tunnel to achieve an internal product temperature in the range xe2x88x923 to xe2x88x925xc2x0 C., typically about xe2x88x924xc2x0 C. The product may be dusted with seasoning and/or seasoning elements and frozen. The product will usually be sold and cooked by the consumer from frozen.
According to another aspect of the present invention there is provided an apparatus for making an helical food product in accordance with the present invention, which apparatus comprises a nozzle for extruding one or more plastic food substrates; a hollow shaping part that is arranged to receive the substrate(s) from the nozzle, said shaping part having an open end downstream of the nozzle; rotating means for causing or allowing relative rotation of the nozzle and shaping part so as to form the substrate(s) into a product of helical configuration; and dispensing means for dispensing a fluid barrier agent onto the outer surface of the helical product as it debouches the nozzle, which fluid barrier agent is adapted to prevent re-annealing of adjacent turns of the helical product; the arrangement being such that in use said helical product is formed within the shaping part, is coated with said fluid barrier agent and is dispensed continuously from the apparatus via the open end of the shaping part.
Conveniently, said nozzle may be journalled for rotation within the hollow shaping part. Said shaping part may define a generally cylindrical conduit that accommodates the outlet end of the nozzle, which conduit extends downstream of the nozzle. Said shaping part may comprise a ring that encircles the outlet end of the rotary nozzle.
Preferably, the nozzle and shaping part define an annular space therebetween, which annular space is open at its downstream end, and said fluid dispensing means is arranged to introduce the fluid barrier agent into said annular space, such that in use the barrier agent is delivered from the annular space via the open downstream end thereof onto the helical product as the product debouches the nozzle. Said fluid dispensing means may comprise a port formed in the shaping part, which port is adapted for connection to a pumped supply of said fluid agent.
Typically said nozzle may comprise an elongate, generally cylindrical component that is adapted for rotation about its longitudinal axis, having a chuck at one end for connection to a rotating means such, for example, as the output of a motor.
In some embodiments, the nozzle may comprise a single dispensing passageway for dispensing a plastic meat-based substrate into the shaping part. Said dispense passageway may be configured such that the substrate is directed outwardly at an angle to the axis of rotation as it debouches into the shaping part, so as to assist in forming the substrate into an helical configuration. The cylindrical component may thus be provided with a longitudinal axial bore, which bore has an inlet at one end for connection to a pumped supply of said food substrate, and an outlet at the other for debauching the substrate interiorly of the shaping part. The axial bore may be deflected away from the longitudinal axis towards the outlet end, so as to direct the debauching meat substrate towards the inner surface of the shaping part. The end face of the component, in which end face the outlet is formed, may be skewed with respect to said longitudinal axis. Said end face may subtend an angle of 15 to 75xc2x0, preferably 30 to 60xc2x0, with the plane of an orthogonal section through said axis. Said end face may be substantially planar, so as to assist in propelling the dispensed meat-based substrate downstream within the shaping part.
Alternatively, in some embodiments, said nozzle may be equipped with two or more dispense passageways that are arranged juxtaposed one another. Each dispense passageway may have an inlet for connection to a respective pumped supply of a plastic food substrate and an outlet for debauching the food substrate into the shaping part. Each of said outlets may be offset from the axis of rotation of the nozzle to assist in forming the substrates into a multiple helix. Said outlets may be of the same diameter as each other or they may have different diameters depending on the desired characteristics of the product. The cylindrical component may thus be provided with a plurality of substantially parallel, longitudinal, non-axial bores to provide the dispense passageways, which bores are open at each end to provide the respective inlets and outlets.
In a particularly preferred aspect of the present invention, the apparatus in accordance with the invention may have a modular construction comprising a plurality of components which can be assembled in different ways to allow co-extrusion of different numbers of plastic food substrates as required. Said apparatus may thus comprise a first base-block component, one or more second intermediate components, a third outlet component and a plurality of nozzle components; wherein said first and third components can be assembled, optionally with one or more of the second components interposed therebetween, to define a continuous, substantially cylindrical cavity, which cavity is adapted to receive one of said nozzle components for rotation therein; wherein each of said nozzle components has an upstream end, a downstream end and a plurality of longitudinally extending open bores, each of which bores has an outlet at the downstream end of the nozzle component and an inlet, the inlets of the bores being longitudinally spaced from one another; wherein each of said second intermediate components and said nozzle component are shaped to define an annular recess around a respective inlet on the nozzle component when fitted, and each second component comprises a supply means adapted to supply a respective food substrate to said annular recess; wherein said third component and said nozzle component are shaped to define an annular space therebetween, which space is open at its downstream end, and means are provided for supplying a fluid barrier agent to the space; wherein the third component extends downstream of the nozzle component when fitted to form a shaping part; and wherein the first base-block component is adapted to receive an output of a rotating means which can be coupled to the upstream end of a nozzle component when fitted for causing rotation of the nozzle component within the cavity; the arrangement being such that the first and third components can be assembled with one or more of the second intermediate components, and a nozzle component with a corresponding number of bores received within the cavity thus formed, for extruding the corresponding number of plastic food substrates to form an helical product having the corresponding number of helices.
In some embodiments one or both of the first and third components may also be equipped with a supply means for supplying a respective plastic food substrate to a respective one of the bores within the nozzle component.
The nozzle components will normally have different numbers of bores, typically two, three, four, five, etc, When it is desired to extrude a product having a given number of helices within a multiple helix, e.g. a double or triple helix, then the apparatus is assembled using the appropriate number of second intermediate components and a nozzle component having said given number of bores is used.
The present invention thus provides a novel helical meat product that substantially retains its helical configuration through manufacture, sale and cooking, by the application of a fluid barrier agent to the outer surface of the product during its manufacture. Said fluid is usually an oil or an oil/water emulsion and may act by weakening protein bonds formed during solubilisation or mixing of the meat comminutes, thus avoiding weak bonding during subsequent cooking or protein denaturation steps.